We found this circuit for musical instruments in the March 1992 Radio Electronics magazine. The circuit has outputs according to the desired scale from a crystal oscillator at the indicated frequency.
This RCA / GE circuit from the 90s can be applied to any modern operational amplifier. The number...
Found in Popular Electronics from the 90s, this circuit turns off an appliance at the end of the...
Found in documentation from the 90s, this circuit is based on operational amplifiers of the time....